I have been going to a gym for about 6 years now. Since about 2 years ago I have this problem with my legs and biceps. When I do my reps I can't feel any pain in the muscle although I am struggling to do the reps. I don't have the sensation that the muscle is pumped up and right about to explode anymore. I barely feel any pain in the muscle during the workout. If I try to flex the muscle and squeeze very hard again I can't feel any pain in it nor can I get it rock hard as I used to. Do you have any idea why this is happening and what the solution would be?